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Automatic undo management lets you explicitly control undo retention. Through the use of a system parameter (UNDO_RETENTION), you can specify the amount of committed undo information to retain in the database. You specify the parameter as clock time (for example, 30 seconds). With retention control, you can configure your system to enable long queries to run successfully.
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不能很好的理解UNDO_RETENTION,UNDO_RETENTION用来控制被提交的事务的undo 信息在数据库中保存的时间?
With retention control, you can configure your system to enable long queries to run successfully.又怎么理解?
最初由 warehouse 发布
[B][php]
Automatic undo management lets you explicitly control undo retention. Through the use of a system parameter (UNDO_RETENTION), you can specify the amount of committed undo information to retain in the database. You specify the parameter as clock time (for example, 30 seconds). With retention control, you can configure your system to enable long queries to run successfully.
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不能很好的理解UNDO_RETENTION,UNDO_RETENTION用来控制被提交的事务的undo 信息在数据库中保存的时间?
With retention control, you can configure your system to enable long queries to run successfully.又怎么理解? [/B]
如果是10g就很好理解,10g中undo_retention=0时就激活自动undo_retention调优.你可以查v$undostat中的第后一字段...